The project is a study of the responses of single units in primary motor cortex (area 4), primary sensory cortex (areas 1,2, and 3), and areas 5 and 7 of macaca mulatta to wrist flexor and extensor torgue pulses or isolated muscle stretch superimposed on a range of steady torques. The aim is to determine the relationships between cortical response to torque pulses or isolated muscle stretch and steady state torque and the relationships between cortical response to torque pulses or isolated muscle stretch and unit behavior during steady state torque. In connection with this project we have developed a technique which permits stretch of individual muscles in the awake behaving primate by direct application of calibrated force unaccompanied by other stimuli. An external electromagnet applies force to a small piece of permeable metal chronically imbedded in the musculotendinous junction. We are using it to provide relatively pure muscle receptor stimulation, in contrast to torque pulses which stimulate muscle, joint, and cutaneous receptors.